Disk brake

ABSTRACT

An electromechanically actuatable self-boosting disk brake in which a friction brake lining is guided displaceably with a guide whose angle to the brake disk is adjustable via an electric motor to attain brake reinforcement. The angle of the guide is adjusted independently of an actuating device with which the friction brake lining is pressed against the brake disk.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 35 USC 371 application of PCT/DE 01/03597 filed onSep. 19, 2001.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a disk brake having a brake disk. a frictionbrake lining and an actuating device for pressing the lining against thedisc.

2. Description of the Prior Art

Disk brakes, are known per se, have both a brake disk and typically twofriction brake linings disposed one on each side of the brake disk. Thefriction brake linings are received in a brake caliper. Most disk brakesused today are actuated hydraulically; that is, for generating a brakingmoment, the friction brake linings are pressed hydraulically against thebrake disk. It is possible for each friction brake lining to be pressedby a hydraulic piston assigned to it against the brake disk. It isequally possible for one of the friction brake linings to be pressedhydraulically against the brake disk and for the other friction brakelining, by a reaction force transmitted via the brake caliper, to bepressed against the other side of the brake disk. In that case, thebrake caliper is embodied as a floating caliper that is displaceabletransversely to the brake disk.

It has also been proposed that disk brakes be actuatedelectromechanically. In this connection, see International PatentDisclosure WO 96/03301, for example. The actuating force for pressingthe one friction brake lining against the brake disk is exerted againstthe friction brake lining in this case by an electric motor via arotation/translation conversion gear, such as a spindle drive. However,electromechanical disk brakes have the disadvantage that to generate asufficiently high tightening force (this is the force with which thefriction brake lining is pressed against the brake disk) and for fasttightening and release, that is, to attain sufficiently high dynamics, alarge and consequently heavy electric motor is needed. This isundesired, since the disk brake can be only poorly accommodated in theinterior of a vehicle wheel rim, where it is usually placed. Moreover,the disk brake is typically mounted on a wheel carrier and forms anunsprung mass. A high weight of the unsprung mass adversely affects avehicle's road holding ability and is therefore unwanted. Anotherdisadvantage of known electromechanical disk brakes is their high powerconsumption, which puts a considerable burden on an on-board electricalsystem of a motor vehicle.

SUMMARY OF THE INVENTION

The disk brake of the invention has a guide for the friction brakelining whose angle to the brake disk is adjustable. Accordingly, adisplacement direction of the friction brake lining is adjustable in itsangle to the brake disk as the friction brake lining is pressed againstthe brake disk. If the friction brake lining is pressed against therotating brake disk for the sake of braking, the brake disk exerts africtional force on the friction brake lining, which is orientedparallel to the brake disk, in its circumferential or secant direction,and in the direction of rotation of the brake disk. If the guide of thefriction brake lining is adjusted in an angle other than a right anglethat is oblique to the brake disk, then the frictional force exerted bythe brake disk on the friction brake lining causes a force component inthe longitudinal direction of the guide. This force component acting onthe friction brake lining presses the friction brake lining against thebrake disk in addition to the tightening force exerted by the actuatingdevice and thus increases the braking moment of the disk brake of theinvention. The magnitude of the additional pressure force exerted on thefriction brake lining by the rotating brake disk, as a consequence ofthe frictional force between the brake disk and the friction brakelining pressed against it via the guide that is adjustable in its angleto the brake disk, is dependent on the angle at which the guide islocated relative to the brake disk. The additional pressure force causesa brake reinforcement or self-boosting of the disk brake of theinvention; only some of the tightening force of the friction brakelining against the brake disk is brought to bear by the actuatingdevice. The magnitude of the brake reinforcement or self-boosting isadjustable by adjusting the angle of the guide of the friction brakelining relative to the brake disk.

The brake reinforcement of the disk brake of the invention has theadvantage that only slight actuating energy suffices to actuate it.Other advantages are high dynamics upon tightening and release. There isalso the advantage that the magnitude of the brake reinforcement isadjustable by adjusting the guide of the friction brake lining and canalso be varied during the actuation of the disk brake.

According to one feature, the guide for the friction brake lining isembodied as a linear guide, which guides the friction brake liningdisplaceably in the direction of the brake disk. This kind of linearguide can for instance be a rod guide or sliding block guide. The linearguide can but need not necessarily be a rectilinear guide.

According to another feature, the guide is embodied such that thefriction brake lining pressed against the brake disk urges the guide inthe direction of an increasingly larger angle relative to the brakedisk, that is, in the direction of reducing the brake reinforcement. Asa result, self-boosting of the brake reinforcement, which can causeself-locking or in other words blocking of the disk brake, is avoided.This embodiment of the invention makes good meterability of the diskbrake possible and assures the capability in every operating state ofreducing the brake reinforcement with only slight positioning energy, ifany, in fact down to zero.

Because of its brake reinforcement and high dynamics, the disk brake ofthe invention is suitable for an electromechanical actuation. Acomparatively small electric motor with low power consumption and lowweight suffices to actuate the disk brake. The disk brake can be compactand light in weight; its brake caliper including the electromechanicalactuating device is only slightly larger than a brake caliper in ahydraulic disk brake. As a result, the disk brake of the invention canbe accommodated inside a rim of a vehicle wheel.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in further detail below, with reference tothe drawings, in which:

FIG. 1 is a simplified schematic sectional view of a disk brake of theinvention, looking radially at a brake disk; and

FIG. 2, is a modified embodiment of the disk brake of FIG. 1 accordingto the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The disk brake 10 of the invention, shown in the drawing, has a brakecaliper 12, which is embodied as a floating caliper; that is, it isdisplaceable transversely to a brake disk 14. The disk brake 10 isactuatable electromechanically; it has an actuating device 16 with anelectric motor 18 and a spindle drive 20. The electric motor 18 has ahollow shaft 22 which forms a nut, also marked 22, of the spindle drive20. The spindle drive 20 is embodied with low friction as aball-and-screw spindle drive. The nut 22 is in engagement via balls 24with a spindle 26. Driving the nut 22 to rotate displaces the spindle 26in the axial direction. The nut 22 of the spindle drive 20, which is atthe same time the shaft 22 of the electric motor 18, is braced androtatably supported via an axial-conical roller bearing 28 in the axialdirection in a motor and gear housing 30. The motor and gear housing 30is a component of the brake caliper 12. It is also possible for themotor and gear housing 30 to be flanged to the brake caliper 12, forinstance by screwing it on.

A bridge 32, which has a yoke 34 and two legs 36, is secured to an endof the spindle 26 toward the brake disk 14. The bridge 32 is joinedrigidly in the middle of its yoke 34 to the spindle 26. The two legs 36of the bridge 32 protrude from the yoke 34 in the direction of the brakedisk 14. Rollers 38 are supported rotatably on free ends of the legs 36of the bridge 32, toward the brake disk 14; with these rollers, thebridge 32 rests on a side, remote from the brake disk 14, of adisplaceable friction brake lining 40.

The displaceable friction brake lining 40 is disposed between the bridge32 of the actuating device 16 and the brake disk 14 in the brake caliper12. For actuating the disk brake 10, the electric motor 18 is suppliedwith current in a tightening direction, causing the shaft 22 of theelectric motor 18 to rotate. As a result of its rotation, the shaft 22,which is at the same time the nut 22 of the spindle drive 20, displacesthe spindle 26 in the direction of the brake disk 14. Via the bridge 32,the spindle 26 presses the displaceable friction brake lining 40 againstthe brake disk 14. As a result of the pressing of the friction brakelining 40 against one side of the brake disk 14, the brake caliper 12,embodied as a floating caliper, is displaced transversely to the brakedisk 14 and as a result presses a fixed friction brake lining 42,located immovably in the brake caliper 12 on the opposite side of thebrake disk 14, against the other side of the brake disk 14 in a mannerknown per se. The friction brake linings 40, 42 pressed against thebrake disk 14 on both sides exert a braking moment on the brake disk 14;they brake the brake disk 14.

For reducing the braking moment or for completely releasing the diskbrake 10, the electric motor 18 is supplied with current in a reversedirection of rotation, so that the friction brake linings 40, 42 arereleased from the brake disk 14, and the brake disk 14 is freelyrotatable.

The friction brake lining 40 that can be pressed by the actuating device16 against the brake disk 14 is guided displaceably in the brake caliper12 by a guide 44 for the sake of being pressed against the brake disk 14and lifted from the brake disk 14. In the exemplary embodiment of theinvention shown and described, the guide 44 is embodied as asliding-block guide 46, 50. The friction brake lining 40 has a slidingblock 46 that protrudes radially outward relative to the brake disk 14.The sliding block 46 rests in a groove 50 that is made radially in theadjustment wheel 48. The groove 50 forms a sliding-block path, withinwhich the sliding block 46 and thus the friction brake lining 40 can bedisplaced. The adjustment wheel 48 is supported rotatably about animaginary pivot axis in the brake caliper 12. The pivot axis extendsparallel, in the exemplary embodiment shown radially, to the brake disk14. The adjustment wheel 48 has set of teeth 52, in the manner of a gearwheel, on its circumference; the set of teeth 52 is interrupted over acircumferential angle of approximately 90°. Meshing with the set ofteeth 52 of the adjustment wheel 48 is a gear wheel 54, which is mountedin a manner fixed against relative rotation on a power takeoff shaft ofa second electric motor 56. The electric motor 56 can be embodied forinstance as a stepping motor or as a geared motor with a flanged-on(planetary) gear.

A second guide, matching the guide 44 described above, is disposedcongruently on a radially inner side, relative to the brake disk 14, ofthe friction brake lining 40 oriented away from the observer. Thissecond guide is hidden by the friction brake lining 40 and the brakecaliper 12 and is therefore not visible in the drawing. It also has anadjustment wheel, which is rotatable about the same pivot axis as thevisible adjustment wheel 48. A sliding block that is coaxial with thevisible sliding block 46 and that protrudes radially inward from thefriction brake lining 40 relative to the brake disk 14 engages asliding-block path of this hidden adjustment wheel.

The two adjustment wheels 48 are synchronously adjustable together;their sliding-block paths 50 are always congruent, so that the slidingblocks 46 on the radially outer and radially inner sides of the frictionbrake lining 40 are always guided displaceably in the same direction.For the sake of the joint synchronous adjustment, the two adjustmentwheels 48 can be mounted on a common shaft in a manner fixed againstrelative rotation. In the exemplary embodiment shown, the secondelectric motor 56 has a gear wheel 54 on both face ends, and these gearwheels mesh with the set of teeth 52 of the adjustment wheels 48. Thetwo gear wheels 54 of the second electric motor 56 are mounted in amanner fixed against relative rotation on a common power takeoff shaftprotruding from the electric motor 56 on both sides.

By supplying current to the second electric motor 56, the adjustmentwheels 48 on the radially outer and radially inner sides of the frictionbrake lining 40 can be pivoted, thus adjusting the sliding-block path 50in its angle to the brake disk 14.

To explain the function of the adjustable guide 44 of the friction brakelining 40, a rotation of the brake disk 14 in the direction of the arrow58 will be assumed below. For braking, as described earlier above,supplying current to the electric motor 18 causes the actuating device16 to press the displaceable friction lining 40 against the brake disk14. The friction brake lining 40 moves in the direction of thesliding-block path 50 then. The adjustment wheel 48 is rotated, as shownin FIG. 1, such that the sliding-block path 50 extends obliquely to thebrake disk 14 in the direction of rotation 58 of the brake disk 14. As aresult, on being pressed against the brake disk 14, the friction brakelining 40 is displaced obliquely toward the brake disk 14, with acomponent in the direction of rotation 58 of the brake disk 14. Therotating brake disk 14 exerts a frictional force on the friction brakelining 40 pressed against it, which force is oriented parallel to thebrake disk 14, in the circumferential or secant direction and thedirection of rotation 58 of the brake disk 14. Because of thesliding-block path 50 positioned obliquely to the brake disk 14, thisfrictional force brings about a force component in the longitudinaldirection of the sliding-block path 50. This force component in thelongitudinal direction of the sliding-block path 50 in turn causes anadditional pressure force of the friction brake lining 40 against thebrake disk 14, which increases the tightening force of the disk brake 10of the invention. The disk brake 10 has a brake reinforcement orself-boosting; its actuating device 16 produces only some of thetightening force that presses the friction brake lining 40 against thebrake disk 14. The remainder of the tightening force of the frictionbrake lining 40 against the brake disk 14 is brought to bear, asdescribed, by the rotating brake disk 14 as a consequence of thefrictional force between the brake disk 14 and the friction brake lining40, via the guide 44, 50 placed obliquely to the brake disk 14. Theproportion of the tightening force not brought to bear by the actuatingdevice 16 is greater, the farther the sliding-block path 50 is adjustedaway from an orientation perpendicular to the brake disk 14, into thedirection of an increasingly more-acute angle in the direction ofrotation 58 of the brake disk 14. By means of this kind of adjustment ofthe sliding-block path 50, the pressure force of the friction brakelining 40 against the brake disk 14 caused by the frictional forcebetween the brake disk 14 and the friction brake lining 40 increases,thus increasing the brake reinforcement or self-boosting of the diskbrake 10 of the invention. Thus the magnitude of the brake reinforcementor self-boosting is adjustable by adjusting the angle of thesliding-block path 50 to the brake disk 14, or in other words bypivoting of the adjustment wheel 48 by the second electric motor 56.

The adjustment wheel 48 of the disk brake 10 of the invention isdisposed so close to the brake disk 14 that at maximal pressure force ofthe friction brake lining 40 against the brake disk 14 and with maximalwear of the friction brake lining 40, the sliding block 46 is notshifted away via the imaginary pivot axis of the adjustment wheel 48 inthe direction of the brake disk 14. That is, the sliding block 46 isalways located on a side of the pivot axis of the adjustment wheel 48remote from the brake disk 14; in an extreme case, the sliding block 46is coaxial with the pivot axis of the adjustment wheel 48. As a result,the frictional force exerted by the brake disk 14 on the friction brakelining 40 acts upon the adjustment wheel 48 via the sliding block 46with a torque that acts in the direction of an increasingly large anglebetween the sliding-block path 50 and the brake disk 14. The frictionalforce exerted by the brake disk 14 on the friction brake lining 40 thusacts on the adjustment wheel 48 in the direction of reducing the brakereinforcement. Self-boosting of the brake reinforcement is avoided, andthe adjustment wheel 48 can be restored, without moment, in thedirection of a rectangular orientation of the sliding-block path 50 tothe brake disk 14, in which orientation the brake reinforcement is zero.

If the direction of rotation of the brake disk 14 is reversed (if thevehicle is driven in reverse), then upon actuation of the disk brake 10,the adjustment wheel 48 is pivoted in the opposite direction from whatis shown in the drawing. The brake reinforcement of the disk brake 10 istherefore independent of the direction of rotation.

In a distinction from FIG. 1, the disk brake 10 shown in FIG. 2 has twoadjustment wheels 48, instead of one adjustment wheel 48, and they aredisposed side by side. As shown in FIG. 1, the two adjustment wheels 48each have a respective sliding-block path 50, in which a sliding block46 of the friction brake lining 40 rests displaceably. The twoadjustment wheels 48 each have a set of teeth 52, which meshes with agear wheel 54 of the second electric motor 56, so that the twoadjustment wheels 48 are pivotable jointly and synchronously with oneanother.

The sliding-block paths 50 of the two adjustment wheels 48 are in thisway always oriented parallel to one another; they form a parallel guide44, 50 for the friction brake lining 40. As in FIG. 1, in FIG. 2 aswell, besides the two visible adjustment wheels 48 on the radially outerside of the friction brake lining 40, there are two further adjustmentwheels of the same kind, not visible, disposed congruently on theradially inner side of the friction brake lining 40. The parallel guide44, 50 of the friction brake lining 40 of the disk brake 10 shown inFIG. 2 prevents tilting of the friction brake lining 40. The adjustmentof the guide 44 is done in the same way as in FIG. 1 and brings about abrake reinforcement of the kind that has been described in conjunctionwith FIG. 1. To avoid repetition, the description of FIG. 1 can bereferred to for FIG. 2. The same reference numerals are used in FIG. 2for components that are the same.

The foregoing relates to preferred exemplary embodiments of theinvention, it being understood that other variants and embodimentsthereof are possible within the spirit and scope of the invention, thelatter being defined by the appended claims.

1. A self-boosting disk brake (10) comprising a brake disk (14), a friction brake lining (40), an actuating device (16) with which the friction brake lining can be pressed against the brake disk to generate a self-boosting braking moment, and a guide (44, 50) for the friction brake lining (40), the angle of the guide relative to the brake disk (14) being adjustable so that the magnitude of the self-boosting of the brake is adjustable, wherein the guide (44, 50) is embodied as a linear guide, and further comprising a pivotable guide element (48) and a first electric motor (56) for pivoting the guide element (48) independently of the actuating device (16) with which the friction brake lining can be pressed against the brake disk, the guide element (48) including the guide (44, 50) for the friction brake lining (40).
 2. A self-boosting disk brake (10) comprising a brake disk (14), a friction brake lining (40), an actuating device with which the friction brake lining can be pressed against the brake disk to generate a braking moment, and a pivotable guide element (48) for the friction brake lining (40), the angle of the pivotable guide element (48) relative to the brake disk (14) being adjustable and an electric motor (56) for adjusting the angle of the pivotable guide element (48) relative relative to the brake disk independently of the actuating device, wherein the guide element (48) is embodied such that the friction brake lining (40) pressed against the brake disk (14) urges the the pivotable guide element (48) in the direction of an increasingly larger angle relative to the brake disk (14).
 3. A self-boosting disk brake (10) comprising a brake disk (14), a friction brake lining (40), an actuating device with which the friction brake lining can be pressed against the brake disk to generate a braking moment, and a guide (44, 50) for the friction brake lining (40), the angle of the guide relative to the brake disk (14) being adjustable and an electric motor (56) for adjusting the angle of the guide (44, 50) relative to the brake disk, wherein the guide (44, 50) is embodied as a parallel guide, which guides the friction brake lining (40) displaceably substantially parallel to the brake disk (14), wherein the disk brake (10) comprises two common pivotable guide elements (48) which cooperate to define the guide (44, 50) for the friction brake lining (40), said pivotable guide elements (48) being actuated by said electric motor via a gear wheel (54).
 4. A self-boosting disk brake (10) comprising a brake disk (14), a friction brake lining (40), an actuating device (16) with which the friction brake lining can be pressed against the brake disk to generate a self-boosting braking moment, and a guide (44, 50) for the friction brake lining (40), the angle of the guide relative to the brake disk (14) being adjustable so that the magnitude of the self-boosting of the brake is adjustable, wherein the guide (44, 50) is embodied as a linear guide, and further comprising a pivotable guide element (48) and a first electric motor (56) for pivoting the guide element (48) independently of the actuating device (16) with which the friction brake lining can be pressed against the brake disk, the guide element (48) including the guide (44, 50) for the friction brake lining (40), wherein the actuating device (16) with which the friction brake lining can be pressed against the brake disk to generate a self-boosting braking moment comprises a second electric motor (18) and a rotation/translation conversion gear (20) for pressing the friction brake lining (40) against the brake disk (14). 